THE CYCLOSTOMES. CLASS AGNATHA

The lampreys are the most primitive of the true vertebrates, their skeletons being cartilaginous without any true bone, and their skulls hardly differentiated from the vertebral column which forms a simple notochordal sheath. They have no true jaws, no ribs, no shoulder or pelvic girdles, and no paired fins. They are eel-like in appearance, but are easily distinguishable from the true eels and, indeed, from most of the true fishes, by their peculiar jawless sucking mouth situated at the tip of the snout, and, further, from all Gulf of Maine eels by lacking pectoral fins.